| 摘要 |
A semiconductor region with an epitaxial layer extending over the semiconductor region is provided. A first silicon etch is performed to form an upper trench portion extending into and terminating within the epitaxial layer. A protective material is formed extending along sidewalls of the upper trench portion and over mesa regions adjacent the upper trench portion but not along a bottom surface of the upper trench portion. A second silicon etch is performed to form a lower trench portion extending from the bottom surface of the upper trench portion through the epitaxial layer and terminating within the semiconductor region, such that the lower trench portion is narrower than the upper trench portion. A two-pass angled implant of dopants of the first conductivity type is carried out to form a silicon region of first conductivity type along sidewalls of the lower trench portion, while the protective material blocks the implant dopants from entering the sidewalls of the upper trench portion and the mesa region adjacent the upper trench portion.
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